The present work is a review on the quality characteristics of groundwater in Nigeria. The aim was to collate, synthesize and analyse hydrochemical data from available literature in order to evaluate the physical and chemical character, quality and determine the sources of ions. The review process covered four major groundwater sedimentary basins viz Benin, Benue, Niger Delta, Sokoto and the Crystalline Basement Complexes. The issue of saline groundwater in parts of Benue and Niger Delta Basins were given attention. In general, data show that on the average, TDS for the groundwater from the different basins was < 250 mg/l compared to the saline groundwater with average TDS as high as 15700 mg/l. The high salinity was attributed to dissolution of salts and seawater intrusion. Nitrate concentration on the average is high especially, for Sokoto Basin indicating anthropogenic pollution. Descriptive and multivariate statistics together with cross plots indicate that the major geologic controls on the groundwater chemistry are chloride dissolution, weathering (silicate and carbonate) and ion exchange. With respect to agricultural and irrigation purposes, the groundwater are excellent besides the water from the saline groundwater from Benue Basin and the coastal aquifers.

Hydrogeochemical study of the fractured/weathered basement of the Oban Massif, southeastern Nigeria has been carried out. Results indicated that concentrations of major cations and anions exhibited the following order of abundance: Ca>Na>Mg>K and HCO 3 >SO 4 >Cl, respectively, with minor variations across sampling seasons. Ca-Na-Cl-SO 4 and Ca-Mg-HCO 3 water types have been identified as major facies, resultant from congruent influences of weathering (mainly silicates), ion exchange processes, and water mixing.Keywords: groundwater; cation; anion; weathering; ion exchange; Oban massif; Nigeria. Química das águas subterrâneas do Maciço Oban, Sudeste da Nigéria RESUMOEstudo hidrogeoquímico do embasamento fraturado / intemperizado do Maciço Oban, sudeste da Nigéria foi realizado. Os resultados indicaram que as concentrações de cátions e ânions apresentaram a seguinte ordem de ocorrência: Ca> Na> Mg> K e HCO3> SO4> Cl, respectivamente, com pequenas variações entre as estações de amostragem. Os tipos de água Ca-Na-Cl-SO4 e Ca-Mg-HCO3 têm sido identificados como os principais fácies, resultantes de influências congruentes de desgaste (principalmente silicatos), processos de permuta iónica e água de mistura.

Black shales have a great environmental geochemical significance and act as a source of metal enrichment which upon weathering could release trace elements into soil system where they are in turn mobilized and release into surface water and groundwater systems. An investigation of environmental geochemistry of rock, soil and water in parts of Abakaliki, southeastern Benue trough, Nigeria was carried out in order to evaluate the impact of shale bedrock in the soil and water environment. Shale rock, soil and water samples were collected from ten (10) locations within the study area and were analyzed for major and trace elements using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). In situ parameters such as pH, in water was measured in the field. The results shows that Pb is highly enriched while As. Cr, Co, Fe, Ni, Sr, V and Zn are slightly enriched in the shales relative to the global shale average. Similar geochemical trend was observed for surface and subsurface soils. Also, the mean concentration of As, Co. Cu. Mn, Pb and Zn in soils at both depths are higher than the mean concentrations in the shale bedrock in the area of study, implying relative enrichments of these metals in the soils of the study area. In addition, the mean values of Al, Fe, Ti, Cr, Ni, Sr and V in both soil depths are lower than the values recorded in the shale bedrock. Relationship between pH and metal load suggested that the waters are dominantly near neutral to alkaline range suggesting that acidic contaminants do not affect the water quality. The mean concentration of Al, Fe, Mn and Pb in groundwater and surface water was above the regulatory standards indicating contamination of the water. The calculated enrichment factor, anthropogenic inputs, pollution index for soil indicated that the soil are highly contaminated through numerous geogenic and anthropogenic sources with Pb being the most toxic metal with the shale bedrock and the mineral load contained in them as the major contributor of these contaminants..

No abstract

Assessment of heavy metal contents in groundwater in vicinities of dumpsites within the Calabar metropolis was carried out. The dumpsites included those located at Akai-Effa, Anantigha, Bogobiri, LEMNA road and Marina beach. The choice of dumpsites was guided by magnitude of operation, history and longevity as related to possible metal speciation, leachate fate and disperssivity. Studied heavy metals included; Fe, Mn, Cu, Zn, Pb, Cd, Cr, Ni, Co and As. Results and interpretation revealed generally the highest concentration of selected metals to be in the vicinities of the Akai-Effa dumpsite (an abandoned and reclaimed automobile repair and scrap metal dumpsite with a long history of operation). This was followed by the Bogobiri dumpsite with a relatively shorter period of operation but a history of frequent incineration of refuse. Hydrochemical modelling indicated the aqueous species of metals to be predominantly free mobile ions, oxides and hydroxides. Other multi-element complexes were also identified at varying degrees of dominance and these were largely hydrated arsenates. Metal speciation in groundwater was adjudged to be controlled by dumpsites longevity, refuse type and associated activities. Current levels and speciation trend create a need for temporal and spatial monitoring for possible hazard prognosis and human health concerns.